This study will investigate the role of neurohypophyseal vasopressin in the control of ACTH and cortisol secretion and the role of corticotropin-releasing factor (CRF) in the control of vasopressin and ACTH secretion in conscious dogs. Neurohypophysectomy attenuates the ACTH response to hypotension and attenuates the cortisol response to ovine CRF-induced increases in ACTH. The ACTH and cortisol response to nitroprusside-induced clamped decreases in blood pressure and to exogenous ovine CRF infusions will be determined in intact dogs, neurohypophysectomized dogs with continuous vasopressin replacement, and in neurohypophysectomized dogs without vasopressin replacement (diabetes insipidus). This will determine if attenuated ACTH responses to hypotension and attenuated cortisol responses to CRF-induced increases in ACTH in neurohypophysectomized dogs can be restored to normal by alleviating the symptoms of diabetes insipidus. Acute infusions of vasopressin during hypotension in neurohypophysectomized dogs to elevate vasopressin levels observed in intact dogs will be performed to determine if the full ACTH response to hypotension requires large increases in plasma vasopressin. In addition, exogenous ACTH infusions will be used to directly assess the role of vasopressin in adrenocortical sensitivity (cortisol, aldosterone, and adrenal androgen) in conscious dogs. Ovine CRF given i.v. to conscious dogs elevates plasma vasopressin levels. We will infuse CRF with and without hypertonic saline to determine if the vasopressin response to CRF interacts with osmoreceptor input. In addition, dexamethasone blockade will be used to determine if the vasopressin response to CRF, like ACTH, is sensitive to glucocorticoid negative feedback. Since the sequencing and synthesis of CRF, studies of the interaction of CRF and vasopressin have been many. The studies proposed herein will examine the role of the neurohypophysis, vasopressin, CRF, and steroid feedback in the control of the anterior and posterior pituitary and the adrenal cortex.